DCB Method Research Articles

Extraction strategies of PAHs from grilled meat for their determination by HPLC–DAD

Strategies have been used in this work for rapid and precise extraction of polycyclic aromatic hydrocarbons (PAHs) from grilled meat. Samples were pre-extracted with acetonitrile/potassium hydroxide under microwave irradiation, and after dilution with water subjected to two alternative pre-concentration and clean-up methods. In the first method, the extract was treated with hydrophilic deep eutectic solvent (DES) of choline chloride:phenol (1:2, molar ratio), and the extract phase separated by salt-assisted liquid–liquid extraction (SALLE) with acetonitrile. This method was found better than the conventionally used emulsification with tetrahydrofuran. In the other method, a methanolic solution of 1,4-dichlorobenzene (DCB) was injected into the extract when a cloudy solution was obtained due to dispersion of DCB particles. The sorbent with extracted PAHs was collected on bare Fe3O4 nanoparticles; a modification which was faster than the usually opted centrifugation in dispersive solid phase extraction. Matrix polar compounds and proteins were excluded due to low polarity of DES-SALLE combination and non-polar surface of DCB. Linear calibration graphs are obtained in HPLC–DAD in the range 0.1–1000 µg kg−1 of PAHs in both extraction methods (using 10 mL of standard extract). The limits of detection (S/N = 3) of PAHs (determined on tenfold diluted standard extract) were in the range 11–25 ng kg−1 by the DES method and 14–30 ng kg−1 by the DCB method, which were better than obtained by many of currently used extraction methods. The enrichment factors ranged 75–115 in DES extraction method, 60–95 in DCB method. The methods have been applied to the real samples of grilled meat, and the results found by the present methods agreed together and with those found by the standard methods. DES method in combination with SALLE was found more convenient to operate.

Mössbauer study of Andean páramo soil from Ventaquemada, Boyacá, Colombia

Samples of paramo soil for Mossbauer studies down to a temperature of 4.2 K were collected from a sampling site in the municipality of Ventaquemada, district of Montoya, sector of Matanegra. This location is close to Tunja, capital of Boyaca Province, Colombia. Paramo soils often result from weathering of volcanic ash and are rich in allophane and organic matter. The Mossbauer spectra show the iron in all samples to be present mainly as a ferric component that splits magnetically at temperatures below about 20 K into a sextet with a mean hyperfine field of about 44 T and broad resonance lines that indicate a distribution of hyperfine fields. Additionally, weak contributions of hematite, magnetite, goethite, and ferric and ferrous iron in clays, are present as well as a structure-less pattern (collapsed sextet) that appears at low temperatures. The broad magnetically split component represents up to 70% of the iron in the Paramo soils. It is quite stable towards heating the soils, converting to hematite mainly between 600 and 800 °C. This rules out that the component is ferrihydrite, which decomposes already below 400 °C. Presumably, it is attributable to the allophane component in the Paramo soils. Leaching by the DCB method removes this component as well as most of the goethite, but only part of the hematite, whereas oxalate leaching removes mainly the broad magnetically split component attributed to allophane, but leaves hematite, magnetite and goethite largely unchanged. Leaching with H2O2, which oxidises and removes the organic matter, has no effect on the Mossbauer spectra, showing that iron bound to organic substances is practically absent.

EXPERIMENTAL FINDING OF FRACTURE TOUGHNESS CHARACTERISTICS AND THEORETICAL MODELING OF CRACK PROPAGATION PROCESSES IN CARBON FIBER SAMPLES UNDER CONDITIONS OF ADDITIVE PRODUCTION

The relevance of the problem stated in this article is that the development of aerospace technology increased the demand for good quality materials. An important issue is ensuring durability in conditions of longterm loads and in conditions of damage development. One of the criteria that ensure the toughness of the material is crack resistance. The aim of the work is to study the interlayer crack resistance (fracture toughness) under loading under conditions of separation and transverse shear, interlayer strength, as well as the effect of temperature on interlayer strength, mechanical tensile properties. A comparison of the values of interlayer crack resistance GIС (separation) and GIIС (shear) and of mechanical tensile properties and interlayer strength of carbon fiber samples is made. The main methods for studying this problem were the short-beam method, the DCB method, the ENF method. The results of the experimental data were compared with modeling the processes of the appearance and development of cracks in the finite element complexes ABAQUS and Ansys based on the VVCT models, cohesive elements. Deviations from the experiment were found and conclusions were drawn that the point of application of the load had to be shifted from the edge of the sample, which will reduce the initial separation and increase the stiffness of the sample. Due to the fact that the cohesion zone model is very sensitive to input parameters, it is necessary to know many parameters and take into account a large number of factors. The practical importance of this work is to show how to use the VCCT model to obtain the critical load of the germination of the first crack. The research technique can be used for further experiments, including simulation further stratification with low inaccuracy.

Mode I interlaminar fracture behavior of 2D woven ceramic matrix composites

AbstractInterlaminar fracture properties of melt‐infiltrated woven SiC/SiC ceramic matrix composites were investigated using traditional and wedge‐loaded double cantilever beam methods. The two methods produced comparable GIC results for some specimens. The difference in boundary conditions between the two methods appeared to influence the crack propagation path. The DCB method, having free‐end boundary condition, allowed more interaction between the crack and the composite microstructure than the wedge method did. The effect of fiber tow layout sequence had an effect on the interlaminar properties. Higher toughness was observed for the orientation where crack propagation occurs between planes with more transverse tows. Jump‐arrest phenomenon was found to have higher significance on the rising R‐curve behavior than fiber bridging.

Fracture Behavior of Reinforced Composite with Epoxy Laminates using DCB Method

Fracture Behavior of Reinforced Composite with Epoxy Laminates using DCB Method

STUDY OF MANGANESE OXIDES AND HYDROXIDES DITRIBUTION IN SOME CALCAREOUS SOILS IN NINEVEH PROVINCE EXTRACTED BY DIFFERENT DISSOLUTION METHODS.

Forty soil samples from eight profiles were chosen to represent Al-Fadhilia , Kara-Tapa and Al-Hamdania regions, in Nineveh Province . Three selective dissolution methods were used to extract the different manganese phases DTPA , DCB and GAc. The results indicated that GAc, method was effective in extracting manganese adsorbed on calcium carbonates and clay surfaces ranged 38.78 - 47.74 mg.Kg-1 soil, DCB method was effective in dissolving manganese oxides especially in the thin black deposits and in Mn-Fe concretions was in second order ranged 11.78 - 39.9 mg.Kg-1 soil , while DTPA method was the lowest in extracting available manganese ranged 0.9 - 3.34 mg.Kg-1 soil.

THE EFFECT OF SOME PHYSIOCHEMICAL FACTORS ON PEDOGENIC DISTRIBUTION OF MANGANESE IN SOME

Eight soil pedons were chosen. in Nineveh Province to determine the effect of physiochemical factors 0n pedogenic distribution of manganese extracted by DCB method. The results indicated that topography had a significant effect in all studied soils. the highest . manganese values in Al-Hamdania ranged between (40-47) mg.Kg-1. followed by Al-Fadhlia & Kara-Tapa regions ranged between (36-39). (11.6-35) mg.Kg-1 respectively. Soil depth had significant effect in Al-Fadhlia & Al-Hamdania regions with ratio effect of 30% . 50% respectively. CaCO3 had a significant effect in Al-Hamdania region only. Organic matter had a slight effect. Soil fine fraction (silt & clay) had unclear effect in which manganese ranged between 37.2-39.52 mg.Kg-1in Al-Hamdania region. Soil pH had non-significant effect on manganese pedogenic distribution in studied soils. DCB was effective extracting method for Mn-Fe concretions and thin black coatings on red and green mudstone.

Research on Stress Corrosion Sensitivity of C110 Casing in Wellbore Protection Fluid

In the environment of HTHP and high H2S, the sour gas enters into the annulus as a result of various factors, leading to annulus pressure and inducing the risk of the stress corrosion cracking in the oil string or the upper casing. To solve the problem, the environmental fracture toughness of C110 high strength casing steel was tested in the NACE A solution and the wellbore protection fluid in simulated conditions in the CORTEST pressure testing system and homemade HTHP autoclave using NACE DCB method in this paper. Wellbore protection fluid is a corrosion inhibitor for steel in oil pipe and annulus. The results indicate that the environmental fracture toughness KISSC of C110 casing steel is 22.78 MPa•m1 / 2, showing strong environmental cracking sensitivity in the standard NACE A solution. In the wellbore protection fluid under the simulated down hole conditions, where the partial pressure of H2S is 1MPa, the partial pressure of CO2 is 0.6MPa, the total pressure is 48Mpa and the temperature is 110°C, it has good resistance to stress corrosion cracking. It can be concluded that excellent wellbore protection fluid greatly increases the resistance of the material properties to environmental cracking. Research results in the paper provide a reference to the safe operation and management to the annulus pressure well in high sour gas fields.

Modification of Grooved Paulownia Wood Sandwich

Interlaminar behavior of paulownia wood sandwich can be enhanced by grooves arranged on the surface of the paulownia wood core. Three kinds of silane coupling agents are used by three different ways in order to improve the interface furtherly. All the specimens are manufactured by VARIM process. DCB method is used to measure the interlaminar energy release ratio(ERR) between the face sheet and paulownia wood core. By comparing the ERRs, the way that core surface pretreated by agent-added resins gets the most effective improvement. By analyzing the component of the ERRs, the improvement mostly comes from the interfaces of glass fibers and vinyl resins left in the grooves. The adhesion of the vinyl resin and paulownia wood gets little benefit from the coupling agents.

Evaluation of Fiber/Matrix Interfacial Fracture Toughness and Its Contribution to Composite Toughness by Using Two and Four-Fibers Model Composite Specimens

Fiber/matrix interfacial crack propagation behavior was investigated by using a model composite specimen. The model composite specimen used in the present study consists of two fibers bonded by matrix resin, and an interfacial crack can propagate without resin fracture in this specimen. Model composite specimens with an initial crack were successfully fabricated from glass fibers of about 200∼400μm in diameter and vinylester resin. Crack propagation tests were carried out by the DCB method for mode I loading and the ELS method for mode II. The average value of interfacial fracture toughness obtained from model composites with silane-treated fibers was much higher than that with untreated fibers for both mode I and II propagation. Thus, the characteristics of fiber/matrix interfacial crack propagation are successfully evaluated by the present test method. The crack propagation tests were also conducted by using another model composite specimen with four parallel fibers distributed in a square array in the cross section. As expected, fracture toughness of four-fibers model composites in which the crack propagation is a combination of interfacial debonding and matrix fracture was higher than interfacial fracture toughness because of large energy dissipation by matrix fracture. Using the interfacial fracture toughness, Gi, the fracture toughness of four-fibers model composites, Gc, and the fracture surface ratio of fiber/matrix debonding in four-fibers model composites, γi, the fracture toughness of matrix resin, Gm, was estimated on the basis of the rule of mixture, Gc = Giγi + Gm(1 + γi).